The present invention relates to a motor-driven apparatus, and more particularly, to a motor-driven apparatus for use in a camera equipped with a shutter device which is normally maintained in a close position after the termination of an exposure and opened in response to the shutter release operation.
The shutter device of the subject type finds wide use for almost all cameras, except for a single lens reflex camera which is disclosed in U.S. Pat. No. 3,750,543. If a motor-driven camera, in which the such shutter device is so constructed that a film drive motor is driven in association with the closing motion of the shutter device, the motor continues to rotate even after the termination of the film transportation. To avoid this, it is imperative to provide means for stopping the motor simultaneously with the termination of the film transportation. Thus, the motor-driven camera of the prior art includes a first switch which is opened in response to the releasing motion of the shutter device and closed in response to the closing motion thereof, and a second switch connected in series with the first switch and opened in response to the termination of the film transportation, the first and second switches being disposed between the motor and an electric power source. In this case, if the second switch is opened before the shutter device is released, then the motor will be undesirably driven, because the first switch is maintained closed at this stage, while if the second switch is opened after the shutter device has been closed, then the actuation of the motor following the termination of exposure is delayed. For these reasons, the second switch, in general, is so arranged as to be closed in response to the opening and closing motions of the shutter device. In such a case, it is necessary to correlate the film transfer mechanism and the shutter device with the second switch. This, however, results in a complicated construction of the camera.
To solve the above described drawback, a motor-driven camera is proposed in U.S. Pat. No. 3,754,455, wherein the first switch is substituted by a capacitor which is continuously charged for a period during which the shutter device is maintained closed and a semi-conductor controlling circuit rendered conductive when the voltage in the capacitor reaches a given level; while the second switch is opened and closed in association with the motion of the film transfer mechanism only. In this motor-driven camera, the capacitor is continuously charged as long as the shutter device is maintained closed, such that if the second switch is closed upon the termination of the film transportation, the semi-conductor controlling circuit is again rendered conductive, to thereby actuate the motor. Thus, a motor-driving circuit is separately provided in that camera, to the effect that the second switch is once opened upon the termination of the film transportation, and the motor is preliminarily driven for a short period of time by the motor driving circuit separately provided, at the initial stage of the shutter release operation for a subsequent exposure, so that the second switch may be reclosed due to the preliminary driving of the motor. Such a construction, however, is attended with a risk that an unexposed film may be accidentally transported due to the preliminary driving of the motor. To avoid this, it is imperative to provide a special mechanism for positively maintaining the film transfer mechanism inoperative for the duration of the preliminary driving of the motor. The provision of such a special mechanism, however, renders the construction of the camera more complicated.
A self-processing camera is now in wide public use, wherein a motor-driven apparatus is built in and an exposed film is transported to the outside of the camera body by a motor driven mechanism. As is well known, in the self-processing camera, film itself constitutes a positive print, such that there is used a special self-processing film larger in image size than the usual 35 mm film. In order to uniformly expose the entire surface of the film sheet to the light so as to produce a print of a high quality, it is obviously preferable to control the exposure amount by the aperture of the photographic lens, rather than by the use of a shutter which controls the exposure amount in the focal plane of the photographic lens. Thus, a lens shutter system is suited for a self-processing camera. Where there is used a photographic lens of short focal length, the quantity of light incident on the circumferential portion of the plane of the film sheet is lessened, as compared with that on the central portion. This is responsible for the production of a print of an uneven exposure. For this reason, a photographic lens of long focal length is better suited for the self-processing camera. On the other hand, a film transferring mechanism, generally, is disposed close to the film sheet which is subjected to exposure. Thus, in the self-processing camera, the shutter device and the film transferring mechanism are spaced apart from each other by a greater distance than those in a camera in which a 35 mm film is used, and thus a large inter-connecting mechanism is required. From the above described viewpoint, the motor-driven apparatus of the prior art in which the second switch is interconnected with the shutter device and the film transferring mechanism is not suited for a self-processing camera.